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Ultrasonic Testing. دانشگاه آزادواحداهواز دانشکده فنی ومهندسی. Shokoh manesh asghar & Hammori amin supervisor : Dr Moeinifar. Introduction to Nondestructive Testing. Six Most Common NDT Methods. Visual Liquid Penetrant Magnetic Ultrasonic Eddy Current X-ray. - PowerPoint PPT Presentation
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آزادواحداهواز دانشگاهومهندسی فنی دانشکده
Ultrasonic Testing
Shokoh manesh asghar&
Hammori aminsupervisor: Dr Moeinifar
Introduction to Nondestructive Testing
Six Most Common NDT Methods
• Visual• Liquid
Penetrant • Magnetic • Ultrasonic• Eddy Current• X-ray
آزمون فرا صوتيUltrasonic Test
آزمون هاي فرا صوتي كاربرد بسيار گسترده اي درتعيين نقص هاي دروني مواد دارند.
از اين روش مي توان براي تعيين ترك هاي زيرسطحي نيز استفاده كرد.
آزمون هاي فرا صوتي عالوه بر بازرسي قطعاتتكميل شده براي بازرسي كنترل كيفيت مراحل
مختلف توليد قطعاتي همچون ورقهاي نورد شده نيز بكار مي روند.
مباني آزمون فرا صوتي از ايجاد موج هاي صوتي توسط يك ضربان سنج استخراج شده است.
روش مدرن بكار گرفته شده امروزي، التراسونيك Sonaناميده مي شود كه علت اين نامگذاري كلمه
مي باشد كه در التين به معني صوت است.
: سرعت موج
در حالتكلي هر چه
محيط مادي
فشرده تر باشد،
سرعت حركت موج
صوتي در آن بيشتر
است. بنابراين سرعت حركت امواج
صوتي در جامدات
بيشتر از سياالت
مي باشد.
Sound Wavelength :
The distance required to complete a cycle› Measured in Meter or mm
Frequency : The number of cycles per unit time› Measured in Hertz (Hz) or Cycles per second (cps)
Velocity : How quick the sound travels Distance per unit time› Measured in meter / second (m / sec)
f
V
Velocity
Frequency
Wavelength
Sound waves are the vibration of particles in solids liquids or gases
Particles vibrate about a mean position
In order to vibrate they require mass and resistance to change
One cycle
Sound WavesSound Waves
Properties of a sound wave Sound cannot
travel in vacuum Sound energy to
be transmitted / transferred from one particle to another
SOLID LIQUID GAS
Velocity The velocity of sound in a particular material is
CONSTANT It is the product of DENSITY and ELASTICITY of the
material It will NOT change if frequency changes Only the wavelength changes Examples:
V Compression in steel : 5960 m/sV Compression in water : 1470 m/sV Compression in air : 330 m/s
STEEL WATER AIR
5 M Hz
ساختمان : پروب
چندين نوع پروب فرستنده وجوددارد، اما همه انواع آنها داراي
� يا از كريستالي است كه مستقيماطريق پوشش محافظ با ماده مورد
آزمايش در تماس است. ،از كوارتز طبيعي � جنس بلور معموال
تيتانات باريم، نيوبات سرب و سولفات ليتيم مي باشد. ولتاژ پله اي
كوتاه مدتي به كريستال اعمال مي شود.
پروب ها ممكن است قائم يازاويه دار باشند.
: پروب هاي زاويه دار پروب ه�اي زاويه دار ب�راي فرس�تادن موج ه�اي برش�ي ي�ا
موج ه�اي ريلي ب�ه درون قطع�ه تحت بازرس�ي ط�راحي شده اند.
پ�روب همانن�د زاويه اي پ�روب كلي س�اختمان عم�ودي اس�ت ب�ا اين تف�اوت ك�ه بل�ور در قطع�ه
پرسپكسي جاسازي شده است. در فص�ل مش�ترك ك�ه بازگش�تي م�وج ط�ولي
پرسپكس�ي - فل�ز تولي�د مي ش�ود، ممكن اس�ت ب�ه كريس�تال برگ�ردد و عالئم گم�راه كنن�ده اي ب�ه م�اده ك�ار اين از جلوگ�يري ب�راي آورد. وج�ود پ�روب در الس�تيك همچ�ون كنن�ده اي ج�ذب ك�ه اس�ت اين ديگ�ر روش جاس�ازي مي ش�ود. قطع�ه پرس�پكس ب�ه گ�ونه اي ش�كل داده ش�ود ك�ه م�وج برگش�تي چن�دين ب�ار بازت�اب ش�ود و ان�رژي ض�ريب ك�ه آنج�ا از و بده�د دس�ت از را خ�ود وج�ود امك�ان اين اس�ت، ب�اال پرس�پكس ج�ذب
خواهد داشت.
درجه صفر زاویه با را امواج قائم پروبهایمیکنند قطعه وارد عمود صورت به . و
Sound Waveforms Sound travels in different waveforms in
different conditions
•Compression wave•Shear wave•Surface wave•Lamb wave
Compression / Longitudinal
Vibration and propagation in the same direction / parallel
Travel in solids, liquids and gases
Propagation
Particle vibration
Shear / Transverse Vibration at right angles / perpendicular
to direction of propagation Travel in solids only Velocity 1/2 compression (same
material)
Propagation
Particle vibration
Compression v Shear
Frequency
0.5MHz
1 MHz 2MHz 4MHz 6MHZ
Compression
11.8 5.9 2.95 1.48 0.98
Shear• 6.5• 3.2• 1.6• 0.8• 0.54
The smaller the wavelength the better the sensitivity
Sound travelling through a material
Velocity varies according to the material
Compression waves
• Steel 5960m/sec
• Water 1470m/sec
• Air 344m/sec
• Copper 4700m/sec
Shear waves
• Steel 3245m/sec
• Water NA
• Air NA
• Copper 2330m/sec
Surface Wave Elliptical vibration Velocity 8% less than shear Penetrate one wavelength deep
Easily dampened by heavy grease or wet fingerFollows curves but reflected by sharp corners or surface cracks
Lamb / Plate Wave Produced by the manipulation of
surface waves and others Used mainly to test very thin
materials / plates Velocity varies with plate thickness and
frequencies
SYMETRIC ASSYMETRIC
Ultrasonic Sound : mechanical vibration
What is Ultrasonic?Very High Frequency sound – above 20 KHz
20,000 cps
Acoustic Spectrum
0 10 100 1K 10K 100K 1M 10M 100m
Sonic / Audible
Human
16Hz - 20kHz
Ultrasonic
> 20kHz = 20,000Hz
Ultrasonic Testing
0.5MHz - 50MHz Ultrasonic : Sound with frequency above 20 KHz
Frequency Frequency : Number of cycles
per second
1 second
1 cycle per 1 second = 1 Hertz
18 cycle per 1 second = 18 Hertz
3 cycle per 1 second = 3 Hertz
1 second 1 second
THE HIGHER THE FREQUENCY THE SMALLER THE WAVELENGTH
Frequency 1 Hz = 1 cycle per second 1 Kilohertz = 1 KHz =
1000Hz 1 Megahertz = 1 MHz = 1000
000Hz
20 KHz= 20 000 Hz
5 M Hz=
5 000 000 Hz
Pg 21
Ultrasonic Inspection
defect
0 10 20 30 40 50
defect echo
Back wall echo
CRT DisplayCompression Probe
Material Thk
initial pulse
Basic Principles of Ultrasonic TestingThe distance the sound traveled can be displayed on the
Flaw DetectorThe screen can be calibrated to give accurate readings of the distance
Bottom / Backwall
Signal from the backwall
Basic Principles of Ultrasonic TestingThe presence of a Defect in the material shows up on the screen of the flaw detector with a less distance than the
bottom of the material
The BWE signal
Defect signal
Defect
The depth of the defect can be read with reference to the marker on the screen
0 10 20 30 40 50 60
60 mm
Thickness / depth measurement
A
A
B
B
C
C
The THINNER the material the less
distance the sound travel
The closer the reflector to the
surface, the signal will be more to the left of the screen
The thickness is read from the screen
684630
Ultrasonic Inspection
0 10 20 30 40 50
initial pulse defect echo
CRT Display
sound path
Angle Probe
defect
Surface distance
The Sound Beam
Dead Zone Near Zone or Fresnel Zone Far Zone or Fraunhofer Zone
The Sound Beam
NZ FZ
Distance
Intensity varies
Exponential Decay
Main Beam
Main Lobe
Side Lobes
Near Zone
Main Beam
The main beam or the centre beam has the highest intensity of sound energyAny reflector hit by the main beam will reflect the high amount of energy
The side lobes has multi minute main beams
Two identical defects may give different amplitudes of signals
Sound Beam
Near Zone Thickness
measurement Detection of
defects Sizing of large
defects only
Far Zone Thickness
measurement Defect detection Sizing of all
defectsNear zone length as small as possible balanced against acceptable minimum detectable defect size
Near Zone
V
fD
f
V
D
4Near Zone
4Near Zone
2
2
Near Zone What is the near zone length of a 5MHz
compression probe with a crystal diameter of 10mm in steel?
mm
V
fD
1.21
000,920,54
000,000,510
4Near Zone
2
2
Near Zone
The bigger the diameter the bigger the near zone
The higher the frequency the bigger the near zone
The lower the velocity the bigger the near zone
V
fDD
4
4Near Zone
22
1 M Hz 5 M Hz
1 M Hz
5 M Hz
Which of the above probes has the longest Near Zone ?
Beam Spread In the far zone sound pulses spread out
as they move away from the crystal
Df
KV
D
KSine or
2
/2
Beam Spread
Df
KV
D
KSine or
2
Edge,K=1.2220dB,K=1.08
6dB,K=0.56 Beam
axis or Main Beam
Beam Spread What is the beam spread of a 10mm,5MHz
compression wave probe in steel?
o
Df
KVSine
35.7 1278.0
105000
592008.1
2
1 M Hz 5 M Hz
1 M Hz
5 M Hz
Which of the above probes has the Largest Beam Spread ?
Beam Spread
The bigger the diameter the smaller the beam spread
The higher the frequency the smaller the beam spread
Df
KV
D
KSine or
2
Which has the larger beam spread, a compression or a shear wave probe?
Ultrasonic Pulse A short pulse of electricity is applied to
a piezo-electric crystal The crystal begins to vibration increases
to maximum amplitude and then decays
Maximum
10% of Maximum
Pulse length
Pulse Length
Pulse Length The longer the pulse, the more
penetrating the sound The shorter the pulse the better the
sensitivity and resolution
Short pulse, 1 or 2 cycles
Long pulse 12 cycles
Pulse Length
Ideal Pulse Length
5 cycles for weld testing
ResolutionRESOLUTION in Pulse Echo Testing is the ability to separate echoes from two or more closely spaced reflectors.
RESOLUTION is strongly affected by Pulse Length:
Short Pulse Length - GOOD RESOLUTIONLong Pulse Length - POOR RESOLUTION
RESOLUTION is an extremely important property in WELD TESTING because the ability to separate ROOT GEOMETRY echoes from ROOT CRACK or LACK OF ROOT FUSION echoes largely determines the effectiveness of Pulse Echo UT in the testing of single sided welds.
Resolution
Good resolution
Resolution
Poor resolution
Scatter The bigger the
grain size the worse the problem
The higher the frequency of the probe the worse the problem
1 MHz 5 MHz
Inclined incidence(not at 0o)REFRACTIONInclined incidence(not at 0o)REFRACTION
The sound is refracted due to differences in sound velocity in the 2 materials
Snell’s Law
C
Perspex
Steel
C
20
48.3
2 Materialin
1 Material
Vel
inVel
RSine
ISine
5960
2730
48.3
20
Sine
Sine
4580.04580.0
Snell’s Law
C
Perspex
Steel
C
15
34.4
2 Materialin
1 Material
Vel
inVel
RSine
ISine
5960
2730
R
15
Sine
Sine
2730
596015SinSinR
565.0SinR
4.34R
Snell’s Law
C
Perspex
Steel
C
20
S
48.3
24
1st Critical Angle
C
27.4
S
33
C Compression wave refracted at 90 degrees
2nd Critical Angle
C
S (Surface Wave)90
C
Shear wave refracted at 90 degrees
57
Shear wave becomes a surface wave
1st Critical Angle Calculation
C
Perspex
SteelC
5960
2730
90
I
Sine
Sine
5960
2730SinI
458.0SinI
26.27I
S
190 Sin
27.2
C
Perspex
Steel
C
3240
2730
90
I
Sine
Sine
3240
2730SinI
8425.0SinI
4.57I
S190 Sin
57.4
2nd Critical Angle Calculation
Sound at an Interface Sound will be either transmitted
across or reflected back
Reflected
Transmitted
Interface
How much is reflected and transmitted depends upon the relative acoustic impedance of the 2 materials
Acoustic Impedance Definition
The Resistance to the passage of sound within a material
Formula
VZ
• Measured in kg / m2 x sec
• Steel46.7 x 106 • Water 1.48 x
106
• Air 0.0041 x 106
• Perspex 3.2 x 106
= Density , V = Velocity
% Sound Reflected at an Interface
reflectedZZ
ZZ%100
2
21
21
% Sound Reflected + % Sound Transmitted = 100%Therefore
% Sound Transmitted = 100% - % Sound Reflected
How much sound is reflected at a steel to water interface?
• Z1 (Steel) = 46.7 x 106
• Z2 (Water) =1.48 x 106
reflected%10048.17.46
48.17.462
reflected%10018.48
22.452
reflected%88.0910093856.0 2 =´
How much sound transmitted?
100 % - the reflected sound
Example : Steel to water
100 % - 88 % ( REFLECTED) = 12 % TRANSMITTED
The BIGGER the Acoustic Impedance Ratio or Difference between the two materials: More sound REFLECTED
than transmitted.
Steel
AirSteel
Air
Steel
Steel Aluminum
Steel
Large Acoustic Impedance Ratio
Large Acoustic Impedance Ratio
No Acoustic Impedance Difference
Small Acoustic Impedance Difference
Interface Behaviour
Similarly:
At an Steel - Air interface 99.96% of the incident sound is reflected
At a Steel - Perspex interface 75.99% of the incident sound is reflected
1
010..20H
HLogdB
2 signals at 20% and 40% FSH.
What is the difference between them in dB’s?
2..2020
4020 1010.. LogLogdB
3010.020dB
dBdB 6
1
010..20H
HLogdB
2 signals at 10% and 100% FSH.
What is the difference between them in dB’s?
10..2010
10020 1010.. LogLogdB
120dB
dBdB 20
Amplitude ratios in decibels 2 : 1 = 6bB 4 : 1 = 12dB 5 : 1 = 14dB 10 : 1 = 20dB 100 : 1 = 40dB
SIZING METHODS 0O PROBE
There are four main sizing techniques used with 0o probes:
• 6 dB drop
• Maximum Amplitude
• Equalisation
• DGS
6 dB Drop
For sizing large planar reflectors only Signal / echo reduced to half the height Example:
› 100% to 50%› 80% to 40%› 70% to 35%› 20% to 10%
› Centre of probe marked representing the edge of defect.
6 dB Drop
BWEDefect
The back wall echo reduced as some part of the beam now striking the defect
The echo of the defect has NOT yet maximise as the whole beam Not yet striking the defectPlan View
6 dB Drop
Plan View
Now the whole beam is on the defect
Defect
Back wall echo is now may be reduced or disappeared
6 dB DropBWEDefe
ct
Plan View
The probe is moved back until the echo is reduced by half of it’s original heightAt this point the probe centre beam is directly on the edge of the defectThe probe is then removed and the centre is marked, and repeat to size the whole defect
Maximum Amplitude Technique
For sizing multifaceted defect – eg. crackNot very accurate Small probe movement
Maximum Amplitude
The whole probe beam is on the defect
At this point, multipoint of the defect reflect the sound to the probeThe echo (signal) show as a few peaks
Multifaceted defect : crack
Maximum Amplitude
Multifaceted defect : crack
The probe is moved out of the defect, the signal disappearedIf the edge of the beam strike the edge of the defect, a very small echo appears
If the probe is moved into the defect, the signals height increase
At this point the MAIN BEAM is directly at the edge of the defect
One of the peak maximised
Maximum Amplitude
The probe is to be moved to the other end of the defect
The signals will flactuate as the beam hits the different faces of the defectsThe probe is moved back into the defect and to observe a peak of the signal maximises
Mark the point under the centre of the probe which indicates the edge of the defectThe length of the defect is measured
Length
Remember: The peak which maximised does not have to be the tallest or the first
one
Equalization Technique
At this point the whole beam is on the back wall
BWE
At this point the whole beam is on the defect
The BWE is at it maximum
The Defect echo is at it maximum
Defect
At the edge of the defect, half of the beam is on the defect, and another half is on the back wall
The defect echo is at equal height as the back wall
The point is marked as the edge of defect
The equalization technique can ONLY be used if the defect is halfway the thickness
Ultrasonic Displays A scan
The CRT (Cathode Ray Tube) display
The Horizontal axis :Represents time base / beam path length / distance / depth
The Vertical axis : Represent the amount of sound energy returned to the crystal
Ultrasonic Displays B scan
The End View Display
B
Ultrasonic Displays C scan
The Plan View Display
C
Ultrasonic Displays D scan
The Side View Display
D
Ultrasonic Test Methods
Pulse Echo Through Transmission Transmission with Reflection
(pulse echo techniques where the transmitter is separate from the receiver - e.g. tandem testing, time of flight)
Pulse Echo Technique
Single probe sends and receives sound
Gives an indication of defect depth and dimensions
Using Ultrasound for Testing:PULSE ECHO
Using Ultrasound for Testing:PULSE ECHO
Using Ultrasound for Testing:PULSE ECHO
Using Ultrasound for Testing:PULSE ECHO
Through Transmission Testing Transmitting and receiving probes on opposite sides of the specimen
Pulsed or Continuous sound Presence of defect indicated by
reduction in transmission signal No indication of defect location Easily automated Commonly integrated into plate
rolling mills - lamination testing
Through Transmission Technique
Transmitting and receiving probes on opposite sides of the specimen
Tx Rx
Presence of defect indicated by reduction in transmission signal
No indication of defect location
Transmission with Reflection
RT
Also known as:
Tandem Technique or
Pitch and Catch Technique
Transmission with Reflection
T R
TANDEM TESTING
Gap Scanning
Probe held a fixed distance above the surface (1 or 2mm)
Couplant is fed into the gap
Immersion Testing Component is placed in a water filled
tank Item is scanned with a probe at a
fixed distance above the surface
Immersion Testing
Immersion Testing
Water path distance
Water path distance
Front surface Back surface
Defect
Using Ultrasound for Testing
PULSE ECHO
450
450
40
40
ULTRASONIC EXAMINATION OF
WELDS
DOUBLE SIDED “T” JOINT
BACK GOUGE
ULTRASONIC EXAMINATION OF
WELDS
00
00
100 (appro
x.)
COVERAGE OF FUSION
FACES
COVERAGE OF WELD VOLUME
450
45 0
450
45 0
COVERAGE OF FUSION
FACES
COVERAGE OF WELD VOLUME
ULTRASONIC EXAMINATION OF
WELDS
SCANNING FOR TRANSVERSE IMPERFECTIONS
450
SCANNING FOR TRANSVERSE IMPERFECTIONS
THREADLIKE DEFECTS, POINT DEFECTS AND FLAT PLANAR DEFECTS ORIENTATED NEAR-
NORMAL TO THE BEAM AXIS ALL PRODUCE AN ECHO RESPONSE WHICH HAS A SINGLE PEAK:
THESE DEFECTS CAN BE DIFFERENTIATED BETWEEN BY OBSERVING THE ECHO DYNAMIC BEHAVIOUR IN LENGTH AND DEPTH SCANS:
POINT THREADLIKE PLANAR(NEAR NORMAL INCIDENCE)
DEPTH SCAN
LENGTH SCAN
NOTE: THE RESPONSE FROM A PLANAR DEFECT WILL BE STRONGLY AFFECTED BY PROBE ANGLE WHILE THAT FROM A THREADLIKE REFLECTOR WILL REMAIN ALMOST UNCHANGED IF A DIFFERENT PROBE ANGLE IS USED.
THE ECHO RESPONSE FROM A LARGE SLAG INCLUSION OR A ROUGH CRACK IS LIKELY TO
HAVE MULTIPLE PEAKS:
SOMETIMES IT WILL BE POSSIBLE TO DIFFERENTIATE BETWEEN THESE 2 DEFECTS SIMPLY BY PLOTTING THEIR POSITION WITHIN THE WELD ZONE:
A. PROBABLE SLAG, POSSIBLE CENTRELINE CRACK
B. PROBABLE HAZ CRACK
IN CASE “A” IT WILL BE DIFFICULT TO DETERMINE WHETHER THE DEFECT IS SLAG OR A
CRACK.
“ROTATIONAL” OR “ORBITAL” PROBE MOVEMENTS MAY HELP:
ORBITAL ROTATIONAL
CRACK SLAG
ORBITAL SCAN
ROTATIONAL SCAN
TYPICAL ECHO DYNAMIC PATTERNS
Calibration Blocks and Their Usage
I.I.W (International Institute of Welding) Block / V1 / A2 Block
100mm
300mm
91mm 85mm
200mm
50mm Dia Perspex
5mm
10mm
15mm
35mm1.5mm Dia
15mm
100mm
23mm 25mm
USESCompressional
Shear
A4 / V2 / DIN 54/122 / KIDNEY BLOCK
R50R2512.5mm or 20mm
PLAN VIEW1.5 OR 5mm dia. hole
USES
i. Calibration
This block can be purchased having a thickness of either 12.5mm or 20mm.b) Shear Probes
a) Compressional Probes
i. Calibration
When aiming at 25mm radius, signals occur at 25, 100, 175, 250, etc.
When aiming at 50mm radius, signals occur at 50, 125, 200, 275, etc.
ii. Index Point
Aiming at 25mm or 50mm radius, maximise signal and mark index.
iii. Probe Angle
By maximising echo from either 1.5mm or 5mm diameter hole and reading off engraved
on side of test block.